Vehicles utilizing automatic or automated mechanical transmissions (also referred to as automated manual transmissions), such as trucks, buses, and cars, depend on gear shifting logic or algorithms to determine the appropriate gear to use for a wide variety of conditions. Each shift decision may be based on a balance between fuel efficiency and performance to provide a desired driving experience. One of the significant parameters impacting this balance is the total mass or weight of the vehicle. For example, a truck carrying no payload may shift to a higher gear by skipping one or more gears to improve fuel efficiency and yet still maintain an adequate level of performance. However, a truck carrying a relatively heavy payload may up-shift through each gear and engage each gear for a longer period of time to improve performance by transmitting an increased amount of power from the engine.
Some systems rely on the equation for Newton's second law of motion, force=mass×acceleration, to calculate a vehicle's mass or weight for use in a shifting algorithm. For example, the force is related to the engine torque, which propels the vehicle. When the engine torque is known, the vehicle mass may be derived through a calculation based on the vehicle's acceleration. A system may repeat the calculation several times to provide a mass or weight value with a better accuracy.
However, the vehicle must be in motion for this mass determination method to work because it requires measurement of a useful acceleration value. Also, this method typically uses an average of several calculations, and a single inaccurate calculation may adversely impact the mass or weight value. Furthermore, collecting and averaging several calculations takes time during which shifting performance may be negatively affected.